Ultra thin absorbers for the hot carrier solar cell applications are promising. Indeed, in these ultimate absorbers electron-phonon scattering are reduced and thickness can be lower than the electron mean-free-path. In this case carriers reach contact ballistically. However it is important that the contact permits to extract these carriers. This theoretical study is about the extraction of the photogenerated carriers and particularly the ballistic extraction without any scattering. We show that quantum interaction between the ultra-thin absorber and the contact can be used to enhance the extraction. Particularly, a contact composed of a quantum well into a double barrier permits to increase the current compared to a simple contact. This improvement is due to a quantum resonance. This result is interesting for the hot carrier solar cells but also for all the ultra-thin cells.